Pharmaceutical blister

ABSTRACT

The present invention relates to a new pharmaceutical blister with reduced permeability to water vapor and gas. It is proposed according to the invention to coat conventional blisters with a silicon oxide-containing functional layer to protect against gases, water vapor and organic molecules.

The present invention relates to a new pharmaceutical blister withreduced permeability to water vapor and gas. The invention proposescoating conventional blisters with a functional layer containing siliconoxide and carbon to protect against gases, water vapor and organicmolecules.

PRIOR ART

Pharmaceutical blisters as packaging for pharmaceutical formulationsserve to package tablets, capsules or other forms of pharmaceuticalssafely and protect them from external environmental influences whichmight in certain circumstances affect the pharmaceutical quality of theformulations. In this context, water or water vapor should be mentionedin particular. If water penetrates into the interior of a blister it maycause lasting changes to the pharmaceutical quality of the drug storedtherein. There is also the danger that volatile substances will diffuseout of the material contained in the blister during storage and therebyalter the pharmaceutical formulation. In addition, the blisters must beso designed that the atmospheric conditions inside them remain constant,e.g., in respect of inhalable preparations, so as not to alter theirparticle size distribution.

Typical blisters consist of at least two films or foils which in turnmay be made up of a number of layers of different or identicalmaterials. On the one hand there is the base layer or base foil and onthe other hand there is a cover layer or cover foil.

One or more wells may be formed in the base foil in which thepharmaceutical formulation, e.g., tablet(s), coated tablet(s) orcapsule(s) can be placed.

The cover foil is placed on the base foil and attached thereto. The twolayers are tightly joined together, e.g., by adhesive bonding, at leastat the edges. The foils are generally made from plastics or metal orcombinations thereof (so called laminates or composite foils). Othermaterials such as paper, for example, may also be used, possibly inaddition.

Preferred blisters consist of transparent or at least translucentplastics or a base foil of transparent plastics and a cover foil ofaluminum. Both foils may be laminates, i.e., they may consist of anumber of foils of different materials. The blisters known from theprior art do not necessarily adequately protect a formulation embeddedtherein from the penetration of substances from outside such as, forexample, gases or vapors, particularly oxygen, carbon dioxide, watervapor and solvents, even when they are mechanically intact.Theoretically, these substances may permeate or diffuse through the topside of the blister (cover foil), the underside (base foil) or throughthe seam between the cover foil and base foil.

To avoid this problem, it is preferable in the prior art to use blistersconsisting only of aluminum foils or aluminum foil laminates. However,these blisters are then no longer transparent and make it virtuallyimpossible to inspect the contents of the blister before opening, e.g.,after the filling process. Therefore, special plastics with high barrierqualities are used for transparent blisters. In most cases, however,special plastics of this kind have only moderate barrier propertiesagainst certain gases, e.g., either against water vapor or againstoxygen, which means that this measure is not satisfactory either.

Processes for improving the barrier against unwanted diffusion ofsubstances which are known from other fields of the art, e.g., thechemical modification of plastic surfaces of petrol tanks bysulphonation or fluorination, have not acquired any significance in thepackaging of pharmaceutical compositions as extensive toxicity andstability tests are required. The prior art also discloses laminatefilms coated with SiO_(x) but because of the rigid layer of SiO_(x)these foils are unable to deform, which means that it is impossible toform wells in order to produce a blister.

In order to achieve a broad barrier effect against gases, water vaporand organic solvents in the case of rigid plastics containers, it isknown to provide the plastics container with a coating of specialorganic and inorganic materials. In this context reference is made tothe article “Multilayer Barrier Coating System Produced byPlasma-impulse Chemical Vapor Deposition (PICVD),” M. Walther, M.Heming, M. Spallek, Surface and Coatings Technology 80 (1996), pp.200-202, which discloses rigid plastics containers having a layer ofSiO_(x)C_(y)H_(z) or TiO_(x)C_(y)H_(z) as barrier layer. The coating isdone by the PICVD process (plasma impulse chemical vapor deposition)which is known for example from DE 40 08 405 C1 and U.S. Pat. No.5,154,943.

Up till now there have been no known comparable processes forpharmaceutical blisters.

DESCRIPTION OF THE INVENTION

An aim of the invention is therefore to provide a transparent, flexible,sealable blister

-   -   1) with improved protection against gas and moisture exchange        between the inside of the blister and the outer environment,    -   2) with sufficient transparency/translucency for visual        inspection and    -   3) sufficient mechanical stability so as not to peel off when        the blister is bent or used.

The disadvantages known from the prior art should also be eliminated.

DETAILED DESCRIPTION OF THE INVENTION

It is proposed according to the invention to coat the base and/or coverfoil of a pharmaceutical blister consisting of plastics with anadditional functional layer containing silicon oxide and carbon, so asto reduce the above-mentioned gas permeability of the actual blister.

If a foil of the blister (preferably the cover foil) consists ofaluminum, it is sufficient to coat the preferably transparent ortranslucent plastics foil (preferably the base foil, as plastics foilscan be more easily deformed than metal foils).

The blister material used for the plastics foils may be PVC (polyvinylchloride), COP (cycloolefin polymer, CZ®), COC (cycloolefin copolymere.g., Topas®), polychlorotrifluoroethylene (e.g., ACLAR®), polyethylene(e.g., in the form of high density polyethylene or low densitypolyethylene), polypropylene, PET (polyethylene terephthalate) and themodifications thereof, polybutene and polymethylpentene, polycarbonates,polyesters, polyacrylates, polyamides or other plastics.

A foil may consist of several layers of the same material or of two ormore layers of different materials (laminates).

A blister may consist of several foils of the same material or two ormore layers of different materials.

Typically, the blister according to the invention consists of a planarcover foil made of aluminum which seals off the deformed (deep-drawn)plastics foil in order to accommodate the pharmaceutical formulation.This (deep-drawn) foil (base foil) is also referred to in the presentcontext as the well foil, as wells or depressions for accommodating thepharmaceutical formulation are typically formed in the foil. Underneaththe (deep-drawn) foil for accommodating the pharmaceutical product analuminum foil may also be formed as an additional foil to prevent waterfrom penetrating through the foil into the (deep-drawn) foil foraccommodating the pharmaceutical product and thereby to minimize thecontact of the pharmaceutical formulation with water or to protect itfrom light. The two aluminum foils may in turn be covered by additionallayers of plastics and/or paper so as to impart increased mechanicalstability to the blister or make printing easier. According to theinvention, the functional layer according to the invention may beapplied to any of the above-mentioned plastics foils.

Preferably, the functional layer is applied to one of the foils locatedclose to the pharmaceutical composition if this option is available.Preferably, on the side nearest the foil adjacent to the pharmaceuticalcomposition. In order that the functional layer is not in direct contactwith the pharmaceutical product another cover layer may be applied tothe functional layer. The functional layer is preferably applied afterthe deformation of the base foil, i.e., after the shaping of the wells.

In this way it is possible to adapt the material of the blister to theparticular contents and the materials for the functional layer to thewell geometry required, the barrier effect, transparency and mechanicalstability.

The blister having at least one plastics film coated according to theinvention is then produced as known in the art. This means that thewells in the base foil are filled with the formulation, then all thefoils are put into position above or below one another and theindividual foils are then welded or glued together. The bonding materialused may be, for example, a heat-sealing lacquer, e.g., based on apolyacrylate and/or polyethylene (e.g., high density and/or low densitypolyethylene) which is typically applied to the cover foil. Thefunctional layer may extend over the entire surface of the correspondingplastics foil of the blister so that part of the functional layer isincorporated in the weld or adhesive seam, or the areas of the plasticsfoil of the blister which form the weld seam or adhesive joint of theblister are free from the functional layer.

Thanks to the functional layer there is a substantially free choice ofplastics material for the blister in order to satisfy other marginalconditions such as, for example, sensitivity to light, color coding,etc.

The silicon oxide-containing functional layer may be applied to all thesurfaces of the plastics layers but preferably to the inside of the baselayer. The thickness of the functional layer is in the nm range (2-500nm), depending on the application, especially in the range from 20-500nm.

The functional layer which contains silicon oxide is preferably a layerthe chemical composition of which varies through the thickness of thelayer and which contains carbon and/or hydrogen and/or titanium aspreferred additional elements.

Preferably, the barrier layer is a carbon-containing silicon oxide layercharacterized by the chemical formula SiO_(x)C_(y), the values of x,yvarying through the layer thickness. The layer may additionally containhydrogen as an impurity, thereby producing the empirical formulaSiO_(x)C_(y)H_(z), while the hydrogen content is kept to a minimum (ztending to 0). Towards the plastics film the layer contains a higherproportion of carbon, C:Si ratio 1:0.5 to 1:5, which merges intoSi-richer areas (C:Si up to 1:10) to change back again into areas with alower Si concentration (C:Si up to 1:0.2).

This latter layer (layer with a very high concentration of carbon) ismost preferably sealable and up to a C:Si ratio of 1:0.2 the layers arestill sufficiently transparent.

According to the invention, in the simplest case the coated foil is a2-ply foil comprising 1) SiO_(x)C_(y)H_(z) and 2) a layer lower incarbon, ideally an SiO₂ layer. In the SiO_(x)C_(y)H_(z) layer thehydrogen content is kept to a minimum (z tending to 0). The layer withless carbon can also be referred as the SiO_(x′)C_(y′)H_(z′). layer,wherein x′ tends to 2, y′ tends to 0 and z′ tends to 0. However, in theinterests of simplicity, this description will refer only to an SiO₂layer.

In another embodiment this sequence of layers is supplemented by anadditional layer component SiO_(a)C_(b)H_(c), so that the SiO₂ layer ispreferably located between this and the SiO_(x)C_(y)H_(z), layer. Inthis way the mechanical stability of the functional layer, particularlythat of the SiO₂ layer, during the bending of the blister and thesealability of the functional layer using heat sealing lacquers isimproved. The SiO_(a)C_(b)H_(c) layer is of analogous construction tothe SiO_(x)C_(y)H_(z) layer, while the value a may differ slightly fromthe value x, i.e., they are not necessarily identical but are of asimilar order of magnitude. The same is true of the analogous pairs ofvalues y and b and z and c. In the SiO_(a)C_(b)H_(c) layer, as well, thehydrogen content is kept to a minimum (c tending to 0). A functionallayer of this kind is preferred, resulting in a layer sequenceSiO_(x)C_(y)H_(z); SiO₂; SiO_(a)C_(b)H_(c). Thus, in a sandwich-likefunctional layer of this type of construction, the C:Si ratio decreasestowards the centre of the layer, ideally until there is a partial SiO₂layer, whereas the two outer layer portions SiO_(x)C_(y)H_(z), andSiO_(a)C_(b)H_(c) have a higher ratio of C to Si. Thanks to this speciallayer sequence which is preferred according to the invention, on thehand a high barrier function against gases and vapors is achieved(primarily by means of the low-carbon inner partial layer) while the twoouter layers SiO_(x)C_(y)H_(z) and SiO_(a)C_(b)H_(c) ensure good bondingor sealing properties of the functional layer.

Thus, the functional layer is able to perform the desired barrierfunction, while the area which has a high Si content, i.e., the areawith a low ratio of C to Si, chiefly takes on the barrier function.

As already indicated, in practice it is preferable not to have a 2- or3-layered sequence with partial layers which are sharply defined fromone another, but rather the individual layers merge into one another. Alayer sequence of this kind may also be referred to as a multi-gradientlayer.

In alternative embodiments, Ti may be used in individual layers insteadof or in addition to Si. Analogously, the SiO_(x)C_(y)H_(z) and/or SiO₂and/or SiO_(a)C_(b)H_(c) layer may be partly or totally exchanged for aTiO_(x)C_(y)H_(z) or TiO₂ or TiO_(a)C_(b)H_(c) layer or such a layer maybe additionally incorporated.

According to the invention the functional layer is preferably applied bythe PICVD method (Plasma Impulse Chemical Vapor Deposition) or by thePECVD process (Plasma Enhanced Chemical Vapor Deposition). This processsurprisingly ensures sufficiently uniform coating of the surface of theblister foil or foils, particularly the well or deep-drawn foil whichhas a highly complex geometry per se because of the number of cavities.The process is preferably a CVD process that is preferably assisted by adownstream plasma.

The coating of the blister foils with a silicon oxide-containingfunctional layer of the sequence SiO_(x)C_(y)H_(z); SiO₂ and optionallySiO_(a)C_(b)H_(c), with or without Si being replaced by Ti, may becarried out analogously to the process known from the prior art. Inconnection with this we refer to the article “Multilayer Barrier CoatingSystem Produced by Plasma-impulse Chemical Vapor Deposition (PICVD),” M.Walther, M. Heming, M. Spallek, Surface and Coatings Technology 80(1996), pp. 200-202, which is incorporated herein in its entirety. Wealso refer to DE 40 08 405 C1 and U.S. Pat. No. 5,154,943, which areincorporated herein in their entirety.

The functional layer may alternatively be applied by sputtering. Again,reference is made here to the prior art. Preferably, however, thecoating is done by the PICVD method with a linear plasma source andcontinuous flow.

The principle of coating by the PICVD method can be described asfollows. The blister foil which is to be coated is placed in a vacuumchamber. Preferably, the surface of the blister foil that is to becoated is warm, for example, from being previously deformed or shaped.The air may be removed from the vacuum chamber which serves as areaction chamber by means of a vacuum pump, e.g., to a pressure of 0.3mbar. Above the vacuum chamber and separated by a microwave window is ahorn microwave antenna. Microwave radiation is pulsed into the vacuumchamber through this microwave antenna. A microwave plasma is thusformed inside the vacuum chamber. The duration of the pulses is anadditional parameter which influences the composition of the layerdeposited.

The microwave pulses, whose duration is in the range from 0.1 to 10 ms,are generated by a microwave generator which is connected to themicrowave antenna via a magnetron. The microwave arrangement typicallyhas standard components of the 2.45 GHz technology.

Both the gas in which a plasma arc is ignited, typically oxygen andinert gases (e.g., nitrogen, argon, helium, hydrogen), and also the gasneeded for producing the coating, the reaction gas, are introducedthrough one or more gas supply arrangements. Typically, the layers ofSiO_(x)C_(y)H_(z) or TiO_(x)C_(y)H_(z) etc. may be built up by means oforganometallic reaction gases such as hexamethyl disiloxane (HMDSO) ortitanium tetraisopropoxide (TIPT), by selecting a suitable pulseduration.

First of all the mixture of oxygen and the reaction gas is introducedinto the vacuum chamber by means of a feed arrangement. Then, by meansof a microwave pulse, a plasma in the vacuum chamber is ignited,cleaving the molecules of the reaction gas. The crack products thusformed diffuse to the nearest surface, i.e., the blister foil andgradually build up the first part of the desired barrier layer. In theinterval between pulses before the next pulse is ignited, which is ofthe order of 100 ms, the spent reaction gases are eliminated from thevacuum chamber by suction in the manner of a 2-stroke engine andreplaced by fresh reaction gas and oxygen.

In order to produce a multiple layer, as soon as the first partial layerof SiO_(x)C_(y)H_(z) has been achieved, the corresponding reactiongas—in this case hexamethyl disiloxane (HMDSO)—is replaced by thereaction gas needed to produce the next partial layer, or the ratio ofreaction gas to oxygen is altered or corrected by the plasmatemperature. In order to produce a smooth transition between thesepartial layers, a mixture of the two reaction gases may be fed in for acertain length of time, for example. For smooth transitions theproportion of the first reaction gas can be reduced and at the same timethe proportion of the second reaction gas can be steadily increased upto the desired value.

If the functional layer is also to contain titanium (Ti), titaniumtetraisopropoxide (TIPT) may be used as the reaction gas, for example.

The light of the plasma is also used to reduce the bacterial count inthe blister contents.

The pharmaceutical blister according to the invention will now bedescribed in more detail with reference to the figures.

FIG. 1 shows a typical blister (1) within the scope of the presentinvention having a plurality of wells, cavities, depressions (2), viewedfrom above.

FIG. 2 diagrammatically shows the principle of the invention insimplified form (without any wells or depressions). A cover foil (10) ofaluminum covers the pharmaceutical capsule (20), this foil being applieddownwards from the functional layer (30) onto a PVC (40)-Aclar (50)composite film.

FIG. 3 diagrammatically shows the principle of the invention in a morecomplex embodiment. In this instance the functional layer is of morecomplex construction. The pharmaceutical capsule (20) is protected fromthe functional layer by a sealing layer (31). The functional layerconsists of three other layers, namely an SiO_(a)C_(b)H_(c) layer (32),an SiO₂ layer (33) and an SiO_(x)C_(y)H_(z) layer (34), applied to thetransparent PVC (40)-Aclar (50) composite film.

FIG. 4 shows a cross section through blister (1), showing only one well(2). The blister consists of a cover foil (100) made of aluminum, then,for example, a deep-drawn foil with a plurality of layers (200, 300,400, 500), which are not connected to one another, for accommodating thepharmaceutical product (20), a lower well foil (400) with a barrierlayer (300) and the protective coating (500) around the lower well foil(400).

Arrows A indicate the cover layer (100) and are intended to representthe route of diffusion of moisture through the cover layer.

The arrows B indicate the base layer (200, 300, 400, 500) and areintended to represent the route of diffusion of moisture through thebase layer.

The arrow C indicates the connecting point between the cover foil andbase foil and the route which moisture can take through this part of theblister.

Each of the layers, particularly the layers 400 or 500, may be coatedwith the barrier coating according to the invention.

Within the scope of the present invention, blisters having the followingsequence of layers are preferred:

A cover foil consisting of a first cover foil (i.e., outermost coverfoil) made of paper (20 to 100 g/m2) or lacquer (0.5 to 3 g/m2), asecond cover layer located below it, consisting of polyethyleneterephthalate, preferably with a thickness of 5 to 20 microns, morepreferably 10 to 15 microns, and finally a layer of aluminum foil with apreferred thickness of 10 to 60 microns, preferably 10 to 50 microns andmost preferably 15 to 40 microns.

Below this is arranged the foil for accommodating the pharmaceuticalproducts, which is formed for example from a 4-ply foil with a preferredthickness of 30 to 500 microns, most preferably 60 to 300 microns. Thisfoil consists initially of a functional layer preferably 20 to 500 nmthick which is sealed off from the pharmaceutical product and which isapplied, on the side in contact with the product, to a PVC film thethickness of which is preferably 10 to 200 microns, more preferably 35to 70 microns, and then an aluminum foil with a thickness of preferably30 to 60 microns, most preferably 35 to 50 microns. This aluminum layeris in turn covered with a layer of polyamide with a preferred thicknessof 10 to 40 microns, more preferably 20 to 30 microns.

Individual layers such as the layer of paper, for example, may beomitted. Any heat sealing lacquers or adhesion promoters needed are notmentioned here in the interests of simplicity.

The most preferred blister consists of two foils, first of all a coverfoil consisting of an aluminum composite foil (preferred thickness 38microns) then a base foil made of PVC (preferred thickness 250 microns),with a silicon oxide-containing functional layer (preferred thickness 20to 500 nm) applied on the side next to the drug. According to theinvention these foils may be welded together so that the aluminum foilis welded or adhesively bonded on the side of the plastics film whichcarries the functional layer according to the invention. Preferably thealuminum foil is welded or adhesively bonded to the plastics film viathe functional layer. Alternatively, the areas of the plastics film ofthe blister which form the weld or adhesive seam of the blister may befree from the functional layer, so that the functional layer does notextend into the weld or adhesive seam.

What is claimed is:
 1. A flexible and translucent foil for apharmaceutical blister pack, the flexible and translucent foilcomprising a flexible, translucent, vapor barrier layer consistingessentially of a carbon-containing oxide having the formula:MO_(x)C_(y)H_(z) wherein M is silicon or titanium, O is oxygen, C iscarbon, H is hydrogen, x≧1, y≧1, and z≧0.
 2. The foil of claim 1, theflexible, translucent, vapor barrier layer comprising a carbon-richlayer component and a carbon-limited layer component, wherein thecarbon-rich layer component has a higher proportion of C to M incomparison to the carbon-limited layer component.
 3. The foil of claim2, wherein the carbon-rich layer component has a first ratio C:M ofabout 1:0.2 to about 1:5, and wherein the carbon-limited layer componenthas a second ratio C:M of at least about 1:5.
 4. The foil of claim 2,the flexible, translucent, vapor barrier layer further comprising asecond carbon-rich layer component, the carbon-limited layer componentbeing disposed between the first and second carbon-rich layercomponents.
 5. The foil of claim 4, wherein the first carbon-rich layercomponent has a first ratio C:M of about 1:0.2 to about 1:5, the secondcarbon-rich layer component has a second ratio C:M of about 1:0.2 toabout 1:5, and the carbon-limited layer component has a third ratio C:Mof about 1:5 to about 1:10.
 6. The foil of claim 1, the flexible andtranslucent foil further comprising one or more materials selected fromthe group consisting of: polyvinylchloride, cycloolefin polymer,cycloolefin copolymer, polychlorotrifluoroethylene, high densitypolyethylene, low density polyethylene, polypropylene, polyethyleneterephtalate, modifications of polyethylene terephtalate, polybutene,polymethylpentene, polycarbonate, polyester, polyacrylate, polyamide,and combinations, composites, and laminates thereof.
 7. The foil ofclaim 6, wherein the flexible and translucent foil is deformed toaccommodate a pharmaceutical product.
 8. The foil of claim 1, whereinthe flexible, translucent, vapor barrier layer has a thickness of about2 to about 500 nm.
 9. The foil of claim 1, wherein the flexible,translucent, vapor barrier layer has a thickness of about 20 to about500 nm.
 10. The foil of claim 1, wherein the flexible, translucent,vapor barrier layer is sealed by a sealing layer, whereby apharmaceutical capsule in contact with the flexible and translucent foilis protected from the flexible, translucent, vapor barrier layer.
 11. Apharmaceutical blister comprising: a substantially planar cover foil;and a base foil comprising a flexible, translucent, vapor barrier layerconsisting essentially of a carbon-containing oxide having the formula:MO_(x)C_(y)H_(z) wherein M is silicon or titanium, O is oxygen, C iscarbon, H is hydrogen, x is an integer and x≧1, y is an integer and y≧1,and z is an integer and z≧0.
 12. The blister of claim 11, wherein thecover foil comprises a layer of aluminum, and wherein the base foilfurther comprises a polyvinylchloride film, the flexible, translucent,vapor barrier layer being applied to the inside of the polyvinylchloridefilm.
 13. The blister of claim 12, wherein the cover foil furthercomprises a first, outermost cover layer of paper or lacquer, and asecond cover layer of polyethylene terephthalate, the layer of aluminumbeing the third, innermost layer, and wherein the base foil furthercomprises an aluminum layer and a polyamide layer, the outside of thepolyvinylchloride film being applied to the inside of the aluminumlayer, and the outside of the aluminum layer being applied to the insideof the polyamide layer.
 14. The blister of claim 13, wherein the secondcover layer of polyethylene terephthalate has a thickness of about 5 toabout 20 microns, the third, innermost cover layer of aluminum has athickness of about 10 to about 60 microns, the flexible barrier layerhas a thickness of about 20 to about 500 nm, the polyvinylchloride filmhas a thickness of about 10 to about 200 microns, the aluminum layer inthe base foil has a thickness of about 30 to about 60 microns, and thepolyamide layer has a thickness of about 10 to about 40 microns, wherebythe deformed base foil has a thickness of about 30 to about 500 microns.15. A method for making a pharmaceutical blister comprising the step ofapplying a flexible, translucent, vapor barrier layer to a flexible andtranslucent foil, the flexible, translucent, vapor barrier layerconsisting essentially of a carbon-containing oxide having the formula:MO_(x)C_(y)H_(z) wherein M is silicon or titanium, O is oxygen, C iscarbon, H is hydrogen, x≧1, y≧1, and z≧0.
 16. The method of claim 15,wherein the flexible, translucent, vapor barrier layer is applied to theflexible and translucent foil using a deposition technique selected fromthe group consisting of: plasma impulse chemical vapor deposition,plasma enhanced chemical vapor deposition, sputtering, or a combinationthereof.
 17. The method of claim 16, wherein the step of applying theflexible, translucent, vapor barrier layer to the foil comprises stepsof: (A) providing a vacuum chamber and a horn microwave antenna inoperable combination; (B) placing the flexible and translucent foil in avacuum chamber and subjecting the flexible and translucent foil to avacuum; (C) introducing an ignition gas and a reaction gas into thevacuum chamber; (D) pulsing microwave radiation into the vacuum chamberthrough the microwave antenna, thereby igniting a plasma in the ignitiongas that cleaves the molecules of the reaction gas, which cleavedmolecules diffuse to the flexible and translucent foil; (E) eliminatingthe spent ignition and reaction gases from the vacuum chamber; and (F)repeating steps (C) through (E) until the flexible, translucent, vaporbarrier layer is applied to a desired thickness on the flexible andtranslucent foil.
 18. The method of claim 17, the reaction gas comprisesan organometallic gas.
 19. The method of claim 18, wherein theorganometallic gas is hexamethyl disiloxane or titaniumtetraisopropoxide.
 20. The method of claim 17, wherein each pulse ofmicrowave radiation has a durations from about 0.1 ms to about 10 ms.